Yes. I am a fan of the Coen brothers. I'm not a fanatic. I'm a big admirer. They create unique worlds and there is a real atmosphere to their films. Not everyone can get that. That's a massive part of their appeal: you can recognise them. Like all the great directors or artists, you know it when you see it.

Although the TV show is different, was there an intention to bring a Coen brothers' sensibility into it?

I think there was. Noah Hawley, who wrote all 10 episodes, was definitely trying to tap into that and I think he did that successfully enough for them to give him their blessing. I don't know the Coen brothers but people I know who do say that's not easily won. But I had no interest in being in just a TV version of the film. As Billy Bob Thornton said: "If it was called Detroit, you'd still have to want to do it."

Thornton is an enigmatic actor surrounded by mythology. Was he like that in person?

Yeah kind of, which I think he enjoys. But he's not a wanker about it. He's a very sweet person. He's a serious person in a way, but he's also funny and likes laughing. I liked him very much immediately.

You obviously enjoy forming partnerships in acting.

Yes I do. I think acting is all about the other people. Sounds like a worthy thing to say but it's true. I like the odd day on my own in the course of a film because you've got complete control and you can indulge yourself and all that sort of stuff. But the best work comes out of at least another person being in the room.

How did you approach acting in a Minnesota accent, which is a long way from Aldershot?

With diligence really, because as you say it's very different from mine. I've got a pretty good musical ear and I can pick things up. But that wasn't going to be good enough. I really wanted to do it justice. Not do it as a sketch: "Oh yah!" So I worked hard at it. I stayed in the accent all day on set. You've got to make it a habit, get that muscle memory.

Fargo subverts the idea of your "niceness". Was that an attraction?

Yes, I'm under no illusion about what I appear like. I just know there's more to me than that as a person, and there's certainly more to me than that as an actor. That's where the frustration comes. My plan was always to be an actor. It wasn't to be a nice guy. I became famous in Britain playing a nice decent guy and that casts a long shadow.

But you must have felt like you've escaped Tim now.

Yes I really do. And it is a great relief, although I'm very proud of The Office. It's one of the best things I've ever done and one of the best things I'll ever do. I don't want to complain about that. Most people don't get anywhere near that kind of reaction and acclaim and for something that you love. So that was a lucky gig.

You have some religious faith. Did you ever get into theological debates with Ricky Gervais, a renowned atheist?

Yeah, we talked about that sort of stuff but it was all lighthearted. He's a very, very intelligent person and in one sense he takes things seriously but in another I don't think he takes anything seriously. We laughed at each other about it. But he's become a lot more professionally atheist.

In 2003, you said you thought we'd reached the zenith of people becoming famous without talent. Were you overly optimistic?

I may have been wrong. I guess it's here to stay. And part of me thinks I should accept it and grow old gracefully and not worry too much about it. You know, apparently when Noël Coward met the Beatles he was very nice to them and said to other people: "They're completely talentless." He was older than I am now but still, you've got to be careful about what you write off because you can be so solid in your knowledge. You don't want to be the person who said the Beatles are talentless.

How did you handle fame after The Office?

I don't know. Amanda [Abbington, his partner] says there was a small period when she felt that I believed it a bit. But I can't remember that, to be honest. It might well be true. But that was also in contrast to where she was at the time. One moment, we're both good jobbing actors and then people are nudging her out of the way at the bar to get to me. That is going to make her feel even more insecure and make me look like I'm being an arrogant prick. I'm not saying I wasn't an arrogant prick. If I was, she says it didn't last long.

Peter Jackson said you were the only actor who could play Bilbo in The Hobbit. To be successful at that level, you've got to feel you're worth it. Have you always had confidence in yourself?

Yes, but there was a period about six or seven years ago where pickings got a bit slimmer, a bit less exciting. I'd just bought a house and then got a tax bill the size of the Isle of Man and I was worried. I remember saying to a very good friend of mine: "Do you think I'm a good actor? Am I just banging my head against the wall?" And I was famous. I'd made Hitchhikers's Guide to the Galaxy but I still kind of thought, maybe that's it. Because you don't know. You don't get a warning. You're not given notice of a year. Then I got another job and I didn't feel like that any more.

Your father died when you were a child. What do you think he would have made of your success?

I think he would have been absolutely proud, but I'm one of five. Whenever someone says to my mum: "How's your son doing?", she says: "Which one?" If you're a parent, you're not going to go: "Oh I'll concentrate on the famous one." I wish he'd met my kids. I wish all sorts of things. I wish I'd got drunk with him. But my family are very proud and that's nice.

Any news on Sherlock?

I don't know. Really. I wish I did. I thought the plan was to do it in the autumn but apparently that's fallen away. We're all busy. But I'm ready. I'm there. It depends if you want to make time for it. I hope we do. I love it.